Ram boring devices of this kind are known and have a striking piston, which is moved pneumatically back and forth in the device housing and in so doing, hits a front-facing or a rear-facing striking surface of the housing, depending on the direction in which the device is moving. The kinetic energy of the striking piston thereby transferred ensures the acceleration of the ram-boring device in the ground, and the creation of a borehole through the radial displacement of the soil.
Such a ram boring device having a control pipe and a striking piston, which can be displaced thereon is known from the German patent application, 39 09 567 A1. The control pipe is connected at the rear end thereof to a pressurized air source, and is connected to a component that is affixed to the housing such that said control pipe can be moved both along the longitudinal axis, and rotated via a pretensioned, exterior helical spring. The above-mentioned helical spring forces the control pipe into a forward motion position and locks said tube in this position after a quarter turn in a front locking groove. When reversing the device from a forward operation to a reverse operation, the control pipe is first unlocked with a quarter turn against the force of the preloaded spring, so that said control pipe is displaced under the influence of the pressurized air (service air) against the spring force exerted in the direction of the longitudinal axis in the reverse operation position thereof. Thus, the reverse operation movement of the striking piston is lengthened resulting in a rear-striking surface that is affixed to the housing being acted upon by the striking piston.
As in the forward operation position, the control pipe is locked in the reverse operation position under the influence of the likewise rotationally pretensioned helical spring in a rear-locking groove. A renewed reversal of the ram boring device back into the forward motion position therefore requires that the control pipe be rotated back and that said control pipe be pushed back into the forward motion position.